The purpose of the research was to obtain an insight into various secondary braking systems for goods vehicles. Practical tests were carried out with a tractor- semi-trailer combination. The performance of various split braking systems as well as spring brake actuators are shown. With nearly all of the secondary braking systems it is possible to obtain sufficient deceleration to meet legal requirements for the braking path. The critical point however is lateral stability. The report concludes with recommendations for legal requirements concerning lateral stability both on dry and on wet road surfaces. It is concluded that: lateral stability must be obtained on both a dry and a wet road surface; tractors for semi-trailers should have a split braking system; and service brakes for motor vehicles and trailers (semi-trailers) should have a certain braking capacity in case a failure occurs (emergency braking capacity). As a solution it is proposed that the emergency braking capacity of the service brake shall be at least 50% of the normal required capacity.
Samenvatting